SIDE PANEL FAN: In or out?

[Mr_Hat]

As I'm sure many of you know, the debate on whether a side panel case fan should be for intake or exhaust is probably one that will never end. Should it be bringing cool air in from outside the case and forcing it towards the CPU and graphics card, or should it be expelling hot air from inside the case? I am determined to make the right choice in the matter so I'm asking the bright minds of Cain's Lair for your input. You can assume that there is also a front-mounted intake fan and a rear-mounted exhaust fan present.

--Mr_Hat

[51ay3r]

I use mine to bring it in down to the cpu and vid card, then my case has intakes on the top (a little strange) and exhausts on the back.

[paceman]

Well since hot air rises, I have my side fans pulling in air and the one on top blowing it out. I think it creates better air flow. But of course it's just MHO.

[PeanutButterSnake{CLR}]

"I'm no expert from recent experience (heck, I have a latop. Have not had a desktop for 6 years now), but when I did have desktops, it always seemed to me that intake fans blowind directly on the CPU and other cards work far better than simply sucking air out."

Ok, that was the typical response. Now here is the PeanutButterSnake(TM) response:

On the intake side of a fun, the air molecules come from all over the place, but especially from near the fan itself. Each molecule moves slowly as it enters the fan. There is not a lot of force on any particular molecule exerted by the fan. There is higher pressure on the air moleclues on the intake side of the fun because they are stuffed closer together. This restricts the airflow from further away. If your fan was sucking out in the side of a case for instance, the air molecules further away, at the actual components, would be hindered somewhat more from entering the fan than the close by air molecules.

BUT as the air molecules go through the fan, they speed up and receive more kinetic energ. They are moving faster obviously than they were on the intake side. The air pressure on the outtake side of the fan is therefore lower.

So, what happens if you apply these physics principles to a computer fan system?

Blowing directly on components is a Good Thing (TM) because you are forcing the molecules to actually REACH the components with their high velocity.

Sucking air from components is not as effective, because you are sucking the many air moleules that were not even recently near the components (plus, air molecules through various slits in your case).

Here is a good analogy: Take a shower. Then dry yourself using these two methods:

1) A fan blowing directly on you.
2) A fan sucking air away from your body.

Q. Which one makes you feel colder?
A. The one that passes more air molecules per second onto the body. Which is #1, a fan blowing directly on you. <there are some evaporation issues in this situation, but the conclusion is the same either way.>

P.S. I don't care whether it's on the side or top or whatever. I was only talking about DISTANCE from the components.

All other things being equal, then the closer the intake fan is to blow on the components, the better. This also assumes you have good airflow in general of course.

[Apache Warrior]

All fans suck. Except when they blow.
Apache

[Pain_Killer{CLR}]

I have 5 case fans ,aside from the psu fans(2)
2 fans in front blowing in
1 side fan blowing in
2 exhaust fans blowing out
psu fans -out

i think there should be a positive pressure air flow,rather than a negative pressure air flow or equal

[Amwryn]

I have 5 case fans ,aside from the psu fans(2)
2 fans in front blowing in
1 side fan blowing in
2 exhaust fans blowing out
psu fans -out

i think there should be a positive pressure air flow,rather than a negative pressure air flow or equal

man... you rig... blows....

[KillerRabbit]

Though PeanutButterSnake makes some good points, one thing that also needs to be considered is what the air flow in your case is like. Personally, I have a nice current that simply goes front to back. It keeps everything at good temps, and even if I add fans, I either see no change or an increase in temps.

So, more info is needed about your setup. The side panel is rather large. Where is your fan? Below the graphics card, around the CPU, dead center? How are your other fans arranged? How many in front and back? One on top? What internal fans do you have?


Always remember, more fans != better cooling. I've known a few people with similar setups as mine and their temps are worse with their 8 case fans that with my 5 fans total.

[Slaughter]

Just open up the side of the case and duct tape a box fan to it and get it over with.

[Mr_Hat]

Just open up the side of the case and duct tape a box fan to it and get it over with.

LOL!

In regards to my particular setup...
12cm intake fan in the front
12cm exhaust fan on the back
9cm intake fan on the side panel (just about level with the CPU)
PSU has an intake fan on the inside, exhaust fan on the outside
Dual fans on GPU with heat pipe
Chipset fan
Standard AMD64 CPU fan
Actually, I have this: http://www.thermaltake.com/xaserCase...mi/swa/swa.htm

[res1492]

All fans suck. Except when they blow.
Apache

Heheheeh.......

[Apache Warrior]

Or run a duct to your case from a window airconditioning unit. That and a couple of exhaust fans are all you need. I have 8 fans total so my computer sucks and blows.
Apache

[fizbanrt]

If you live in a cold-climate area, just put it outside the window....

[ViTO]

It all has to do with air flow in general.
It needs to remain constant through the entire case.

Your cpu & video draw air away from the components, where does that air go ?
Do you want to push that air back to the unit which creates a bottleneck in the over-all flow.

do this.... Get someone who smokes heavy ( he he ) or a can of smoke and blow it into your case. look for dead spots where smoke sits stagnant.

Air should move in from one direction and out from another that could be any direction depending on case design, cabling, components, etc...

There is no set standard to how it SHOULD be.

[Nomadicus]

do this.... Get someone who smokes heavy ( he he ) or a can of smoke and blow it into your case. look for dead spots where smoke sits stagnant.

I have an excellent cigar collection. Perhaps a Fuente Opus Opus X would be the perfect blend of taste and stagnant air detector. I suspect care must be given when introducing smoke into the case by using a fanless opening. Therefore, gently open a side panel to a minimum and with great care, exhale the smoke in a controlled and steady fashion so as to allow the case to fill gradually but only in the section of the opening -- the correct technique should introduce just enough smoke to fill 1/4 of the case and enough time to reclose the side panel allowing the smoke to circulate nearest the front fan. Now watch the smoke drift and swirl looking for patterns of slow movement or none at all. These are your dead spots.

Upon locating these dead spots reorganize the cables and fans for optimal air flow without compromising the areas already adequately cooled. Make sure you have positive pressure within the case by adding yet another intake fan lest this second phase will achieve less then optimal results. Light a second cigar and for this I recommend a Te'amo Maximo in a maduro known for its great nutty and coffee flavor taste as well as high smoke density -- it is simply the perfect Mexican cigar for this occasion. Gently blow the smoke directly into the slowest fan intake allowing for quick swirl and circulation throughout the case. A second observer may be required being as you will want to exhale for a longer period of time then in Phase I above while occasionally puffing a smoke ring the approximate diameter of golf ball or raquet ball depending on the situation (obviously, an 80mm fan only needs the golf ball size and a 120mm fan the raquet ball size smoke ring). The second observer will note any remaining dead spots and recommend appropriate changes.

When all is perfect, go have a drink at your favorite cigar bar celebrating with an Aston Cabinet #7 in a plain wrapper. This cigar is mild, flavorful, and smooth, best enjoyed with some brandy.

Until next time, have a good day frag'n everyone in sight, and we will return with more tips for your PC health and wellness while maintaining the style and sophistication you so richly deserve. Go on, pamper yourself, you won't regret it.

-- nomadicus